Devices are available for vulcanizing the bead zones of a pneumatic tire. They are generally heavy and large in size and stationary in construction. Such devices are constructed with a middle support element for the tire, an electrically heatable pair of tongs, disposed at one end of the support element, where the jaws of said tongs grip the bead point that is to be vulcanized, a hold-up element that is disposed extendably at the other end of the support element and is supported against the diametrically opposite bead point, and means to activate the tongs and to extend the hold-up element.
A prospectus "Bead Repair Press" of Mohawk Rubber Sales Company Inc. describes such an apparatus, in which a plate-shaped support element is mounted on a stand that is anchored on the floor. A slide-like hold-up element is placed on this support element. This hold-up element can be moved by means of a hand lever, via an articulated linkage. Its frontal surface is appropriately profiled, and is supported against a section of that tire bead which is diametrically opposite the portion of the bead that needs repair. At the other end of the plate-shaped support element there are tongs with electrical heating elements built into their jaws. These tongs can be closed and opened by means of a second hand lever, via another articulated lever linkage. Here its two jaws enclose the bead point that needs repair and exert a certain pressure on it during the vulcanization process. The heating cartridges in the jaws are connected, by way of a thermostat, to a patch cord. This apparatus is mounted in a stationary manner and is used to repair pneumatic tires which have been damaged in the bead area. Such damage occurs, e.g., when the tires are improperly mounted on rims, when the tires run up on the edges of curbs, or the like.
Before the vulcanization process, the damaged points are roughened, and the damage funnels are filled with a suitable vulcanizing material with slight superelevation. The pneumatic tire is then placed on the plate-shaped support element so that the bead point being repaired is situated between the jaws. By activating the appropriate hand lever, the hold-up element is then moved so that its profiled frontal surface presses against the bead section which is situated diametrically opposite the bead point being repaired. As a result, the bead paint that is being repaired is solidly pulled between the jaws. Then the second hand lever is activated to close the jaws of the tongs and to exert the highest possible pressure on the bead point that is being vulcanized. Before this, the heating cartridges that are built into the heating jaws are activated, so that the jaws have a temperature of about 150.degree. at their effective outer side. After the somewhat lengthy vulcanization process has been concluded the two hand levers are activated in the opposite direction, and the tire is manually removed from the apparatus.
Especially with large tires, difficulties result in actual practice when lifting them and when inserting them into the apparatus, on account of their dimensions and especially on account of their heavy weight. Furthermore, because hand levers are used for activation, especially for activating the jaws of the tongs, it is not assured that the compressive force necessary for optimal vulcanization has actually been achieved.